In Japan DTP vaccine containing acellular pertussis vaccine totally replaced DTP which contained whole cell pertussis vaccine. Since then acceptance rates of third doses of pertussis vaccine remained over 80%. Pertussis has steadily decreased in Japan. The purpose of this study was to evaluate current acellular pertussis vaccine in Japan. Antibody responses to acellular vaccines were evaluated by the most sensitive ELISA.Secondary attack rates were evaluated. National survey of the pertussis patients was performed by a research team.It was concluded that children given three doses of acellular pertussis vaccine showed antibody responses comparable to those who contracted natural pertussis infection. Studies on secondary attack rates by family contact study revealed the acellular pertussis vaccine was very effective.